Cover photograph (Copyright © 2000, American Society for Microbiology. All rights reserved.): Electron microscopy analysis of Rep-DNA complexes on viral and chromosomal target DNA. His-tagged purified adeno-associated virus Rep protein (Rep68) bound to the two AAV inverted terminal repeats on the AAV genome (magnification, ×9,000) and a 2.7-kb preintegration fragment (chromosome 19, outlined in reddish gray; magnification, ×13,000). All molecules displayed uniform multimeric Rep complex size. The formation of these complexes on target substrates suggests an essential step in AAV type 2 site-specific recombination. (Photograph provided courtesy of Jack Griffith, University of North Carolina at Chapel Hill EM Core Facility.) (See related article in May 2000, issue 9: vol. 74, p. 3953.)